In conventional two-door vehicles, the backrest structure of the vehicle front seat is pivotally mounted for forward tilting movement over the horizontal portion of the seat structure. This is necessary to provide for easier ingress and egress to the rear seat of the vehicle. In compact size vehicles, it has been found necessary to support the backrest structure on curved support arms which are pivotally-connected to the seat structure some distance forwardly of the seat rear edge. Thus, when the backrest is tilted forwardly, it also is bodily shifted upwardly to clear the cushion therebeneath and to open up a greater access aisle to the rear seat area. It is frequently desired to incorporate a mechanism permitting the backrest structure to be rearwardly inclined to provide a recliner seat. This requires that an adjuster be incorporated in the vehicle seat structure.
If the pivot axis about which the backrest structure is forwardly tiltable is located substantially beneath the backrest structure, simple bell crank mechanisms may be adapted to control the rearward recliner positions. Such simple bell crank mechanisms are disclosed in U.S. Pat. No. 3,024,607 issued to M. Brandoli on Mar. 6, 1962 for a "Seat Having Adjustable Back", in U.S. Pat. No. 3,046,055 issued to J. E. Martens on July 24, 1962 for "Position-Adjusting Mechanism", and U.S. Pat. No. 3,062,584 issued Nov. 6, 1962 to S. J. Galla for "Vehicular Seat Assembly".
If the pivot axis of the backrest is located substantially forward of the backrest structure, however, adaptation of simple bell crank mechanisms have been found not to be feasible within passenger compartment packaging restrictions. That is, it is not feasible to conceal the mechanism beneath the seat structure to assure ocupant anonymity of the mechanism.
Accordingly, it is an object of the present invention to utilize a four-bar linkage adjuster mechanism in place of the simple bell crank adjuster mechanisms, the path taken by the four-bar adjuster mechanism being capable of closely approximating the path of the backrest. Despite the effect of the offset pivot axis, this allows packaging of the adjuster mechanism within close proximity of the rear of the seat structure.